300-440 Exam Dumps : Designing and Implementing Cloud Connectivity (ENCC)

 In the given scenario, an engineer is configuring a site-to-site IPsec VPN connection between an on-premises Cisco IOS XE router and AWS. The correct command to complete the tunnel configuration is “tunnel source 20.20.20.21”. This command specifies the source IP address for the tunnel, which is essential for establishing a secure connection between two endpoints over the internet or another network1. References:

• Configure IOS-XE Site-to-Site VPN Connection to Amazon Web Services - Cisco Community
• [Security for VPNs with IPsec Configuration Guide, Cisco IOS XE Release 3S - Config

Step 1 = crypto map cisco 1 ipsec-isakmp Step 2 = set peer 192.168.10.1 default Step 3 = set peer 192.168.20.1 Step 4 = set security-association idle-time 120 default

The process of editing the settings of a site-to-site IPsec VPN connection between an on-premises Cisco IOS XE router and Amazon Web Services (AWS), and configuring IPsec to support multiple peers and failover after 120 seconds of idle time on the first entry of the crypto map named Cisco involves several steps123456.

• crypto map cisco 1 ipsec-isakmp: This command is used to create a new entry in the crypto map named “cisco”. The “1” is the sequence number of the entry, and “ipsec-isakmp” specifies that the IPSec security associations (SAs) should be established using the Internet Key Exchange (IKE) protocol13.
• set peer 192.168.10.1 default: This command is used to specify the IP address of the default peer for the crypto map entry. In this case, the default peer is at IP address 192.168.10.115.
• set peer 192.168.20.1: This command is used to add an additional peer to the crypto map entry. In this case, the additional peer is at IP address 192.168.20.1. This allows the IPsec VPN to support multiple peers56.
• set security-association idle-time 120 default: This command is used to set the idle time for the security association. If no traffic is detected over the VPN for the specified idle time (in this case, 120 seconds), the security association is deleted, and the VPN connection fails over to the next peer46.

References :=

• Configure a Site-to-Site IPSec IKEv1 Tunnel Between an ASA and a Cisco IOS Router - Cisco
• Configure IOS-XE Site-to-Site VPN Connection to Amazon Web Services - Cisco Community
• Configuring Site to Site IPSec VPN Tunnel Between Cisco Routers
• Configure Failover for IPSec Site-to-Site Tunnels with Backup ISP Links on FTD Managed by FMC - Cisco
• Does Setting Multiple Peers in a Crypto Map Also Support Parallel IPSec Connections - Cisco Community
• Multiple WAN Connections — IPsec in Multi-WAN Environments | pfSense Documentation
• Multiple Set Peer for VPN Failover - Server Fault

 BFD (Bidirectional Forwarding Detection) is a protocol that detects failures in the overlay tunnel between Cisco SD-WAN devices. BFD packets are sent and received periodically by each device to check the liveliness and quality of the connection. If a device does not receive a BFD packet from its peer within a specified timeout interval, itconsiders the peer to be unreachable and reports a BFD down event. This event triggers a control connection state change and a possible route change in the SD-WAN fabric.

In this scenario, the engineer discovers that BFD is flapping on vEdge1, which means that the BFD session between vEdge1 and the remote Edge device is going up and down repeatedly. This indicates a connectivity issue between the two devices, such as network congestion, packet loss, or misconfiguration. The most likely cause of the problem is that the remote Edge device failed to respond BFD keepalives within the timeout interval, which resulted in a BFD timeout event on vEdge1. This event caused vEdge1 to mark the remote Edge device as down and notify the control plane. The control plane then tried to establish a new BFD session with the remote Edge device, which may have succeeded or failed depending on the network condition. This cycle of BFD session creation and deletion caused the BFD flapping on vEdge1.

The other options are less likely to be the cause of the problem. Option A is incorrect because if the remote Edge device BFD was down, vEdge1 would not receive any BFD packets from it and would not flap. Option C is incorrect because if the remote Edge device had a duplicate IP address, vEdge1 would not be able to establish a BFD session with it in the first place. Option D is incorrect because the control plane does not delete the BFD session unless there is a configuration change or a port-hop event on the device. References: Bidirectional Forwarding Detection Flap-Reason Definitions on Cisco vEdge Routers, Cisco Catalyst SD-WAN BFD, Cisco SD WAN: BFD (Bidirectional Forwarding Detection)